Witherick, M. E. (1990). Population geography. Longman.
Lua i Stíl Chicago (17ú heag.)Witherick, M. E. Population Geography. London: Longman, 1990.
Lua MLA (9ú heag.)Witherick, M. E. Population Geography. Longman, 1990.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.